1. Field of the Invention
The present invention relates to an ink set suitable for ink jet recording, an ink jet recording method, a recording unit, an ink cartridge, an ink jet recording apparatus, a bleed alleviating method, and a method for improving fixability of a black image.
2. Related Background Art
Conventionally, aqueous inks are used for color recording by using an ink jet recording method. In the aqueous ink a dye of an individual color tone is dissolved in a water-soluble medium. Usually, three color inks of cyan, magenta, and yellow are used.
These inks are required to have not only reliability in an ink jet system, but also to provide sufficient image density, good drying performance, no bleeding, no blotching with water, alcohol and the like, good weather resistance to the recorded image. Particularly, as high quality ink jet images comparable to silver salt photographs have been realized, not only good image quality but also a longer life is required for recorded images.
Since fading by light exposure is a main cause of deterioration of the storage stability of an image, formation of an image having more light fastness is required. When a recorded image produced with an ink is exposed to light, the dye in an image produced with an ink tends to deteriorate by light resulting in fading conspicuous. Hence, light fastness of the image has been improved by using dyes having a structure which is excellent in light fastness for color inks and/or by using a recording medium which can prevent light fading.
However, the color balance of the image tends to be upset when the entire image is exposed to light, and the entire image whose color balance is upset may give the impressin that the quality is worsened. For example, when a multicolor image is formed with cyan, magenta, and yellow inks, and if light fastness of the cyan image is smaller than that of the other two colors, the part formed with the cyan ink will fade more to give a less bluish image after light fading in comparison with the image immediately after printing.
Japanese Patent Application Laid-Open No. 10-329403 discloses an ink set of cyan, magenta and yellow inks, where the respective images"" xcex94E, the images being produced with three color inks, are less than 25, 30 and 15, in a one-year pseudo-fading test with office light. However, a residual rate of reflection density is not discussed for each color, and the respective xcex94Es of the images formed with the respective color inks is large. Thus, the ink set is not said to produce an image having good light fastness. In addition, color balance of a full color image using these three colors is not described showing that the long-term storage stability is not intended. On such a technical background, the present inventors has been motivated to develop a color ink set which will produce images maintaining the color balance after long-term storage, and good image quality.
On the other hand, in order to form a high-quality multicolor ink-jet image, it is an important technical problem to alleviate bleed in a boundary region between a color image and a black image on the recording medium. Various ideas for combinations of color and black inks have been proposed to solve this problem, but it is completely unknown whether those ideas are also effective with the color ink set to produce images maintaining the color balance. There is not known any set of the color ink set and black ink that can alleviate the change of color balance with time as well as bleeding at the boundary.
An object of the present invention is to provide an ink set, which can provide an image with little change in color balance during long time, and at the same time can alleviate in a boundary region between a color image and a black image in a multicolor image.
Another object of the invention is to provide an ink jet recording method which can form a high-quality multicolor image with effectively alleviated bleeding and with a less change in the color balance in time sequence.
A still further object of the invention is to provide a recording unit and an ink jet recording apparatus which can form a high-quality multicolor ink jet recording image with a less change in the color balance in time sequence.
The still further object of the invention is to provide an ink cartridge which can form a high-quality multicolor image with a less change in the color balance in time sequence.
The still further object of the invention is to provide a method for alleviating bleeding in a multicolor ink jet recording image which can form a high-quality multicolor image with effectively suppressed bleeding and with a less change in the color balance in time sequence.
Still further object of the invention is to provide a method for improving fixability of a black image to a recording medium, which can form a high-quality multicolor image with less change in color balance in the color image in time sequence, and can improve fixability of the black image to the recording medium.
In consideration of the above described objects, the present inventors tested various inks and as a result, found that when color inks that provide respective images having a similar light fading (xcex94E) are used as a set, it can prevent image deterioration due to the color balance change after long-term storage. The inventor has also found that bleeding between a black image region and a colored image region can be effectively alleviated while maintaining the above color balance change suppressing effect by using a black ink containing a pigment dispersed in an aqueous medium by the action of the ionic group of the pigment, with the above color ink set but at least one of the color inks contains at least one of a coloring material and an additive that destabilizes the dispersion stability of the pigment in the black ink. This resulted in the achievemetn of the present invention.
According to one aspect of the present invention, there is provided an ink set.
According to another aspect of the present invention, there is provided an ink jet recording method.
According to still another aspect of the present invention, there is provided a recording unit.
According to still another aspect of the present invention, there is provided an ink cartridge.
According to still another aspect of the present invention, there is provided a recording apparatus.
According to still another aspect of the present invention, there is provided an ink set.
According to still another aspect of the present invention, there is provided an ink set.
According to still another aspect of the present invention, there is provided a method for alleviating bleeding.
According to still another aspect of the present invention, there is provided a method.